1. Field of the Invention
The present invention relates to a lighting controlling device of vehicle lighting equipment and, more particularly, a lighting controlling device of vehicle lighting equipment constructed to control lighting of semiconductor light sources constructed by semiconductor for light remitting elements.
2. Background Art
Conventionally, lighting equipment using semiconductor light emitting elements such as LEDs (Light Emitting Diodes) as the light sources has been known as vehicle lighting equipment. A lighting controlling device for controlling the lighting of LEDs is included in the vehicle lighting equipment of this type.
As the lighting controlling device, a device equipped with a current driving portion connected in series with LEDs to control LEDs such that a normal current flows though LEDs, and a switching regulator for controlling an output voltage applied to LEDs at a maximum voltage in response to a controlled state of the current driving portion has been known. The switching regulator can control the output voltage such that a normal current flows though LEDs respectively even when a plurality of LEDs are connected in series or parallel with the switching regulator.
However, when the output of the switching regulator is short-circuited or grounded, a load of the switching regulator becomes heavy, and occasionally failure is caused due to application of an excessive power. Also, when the output of the switching regulator is opened by a disconnection, or the like, sometimes the output voltage rises excessively in the fly-back switching regulator, for example.
Therefore, such a switching regulator has been proposed that the current driving portion controls the semiconductor light sources (LEDs) such that a normal current flows though LEDs and also the switching regulator controls the output voltage applied to the semiconductor light sources (LEDs) at the maximum voltage in response to the controlled state of the current driving portion, and an operation of the switching regulator is stopped when the output voltage is lowered abnormally on account of a ground fault of the anode side of any semiconductor light source (LED) or a short-circuit of the output side of the switching regulator (see Patent Literature 1).
[Patent Literature 1] JP-A-2006-103477 (particularly, p. 4 to p. 6, FIG. 1)